The invention relates, in general, to a method of forming a mask pattern and, more particularly, to a method of forming a mask pattern wherein micro patterns having resolutions lower than those of exposure equipment can be formed by overcoming the resolutions of the exposure equipment.
As semiconductor products are miniaturized and highly-integrated, there is an increasing interest for patterning techniques for forming patterns in order to develop new functions of devices.
A patterning technique having a high level of integration has been developed as a core technique of semiconductor manufacturing, and largely employs a photolithography process.
The photolithography process includes forming a photoresist layer by coating a photoresist, that is, chemical material that reacts to radiation, performing exposure and development processes on the photoresist layer to form a mask pattern, and selectively etching a lower layer by using the formed mask pattern.
In general, the process capability limit (resolutions) of photoresist exposure equipment used for pattern formation is decided by a wavelength of a light source and numerical aperture (NA) of the exposure equipment as in the following Equation 1.
  R  =      kS    ⁢                  ⁢          λ      NA      where, R is resolution, k is a process parameter, λ is a wavelength of the light source, and NA is a numerical aperture.
The resolutions of exposure equipment that has been developed so far are 55 nm on the basis of a half pitch. Thus, there is a need for developing new and expensive exposure equipment in order to form a pattern requiring resolutions that exceed the process capability limit of the existing exposure equipment, that is, a pattern of 50 nm or less.